The present invention relates to an automated analytical apparatus, and more particularly, concerns an automatic analyzer for the chemical or immunochemical testing of substances on a random access basis.
2. Description of the Prior Art.
There are many known and available analyzers for the chemical, immunochemical and/or biological testing of samples. In many instances, chemical tests are performed on biological fluids such as urine, blood serum, plasma, cerebrospinal fluid and the like. A sample of this fluid is typically combined with a prepared reagent liquid, and the resulting mixture, or subsequent mixtures, is analyzed by the apparatus for one or more characteristics of the sample. Reliance on automated clinical or chemical analyzers improves the efficiency of the laboratory procedures inasmuch as the technician typically has fewer tasks to perform than might be required if manual analysis were conducted. Moreover, automated clinical analyzers usually provide results much more rapidly, while also placing emphasis on accuracy and repeatability of the various tests.
A typical automated clinical analyzer available for many routine laboratory tests includes a transport or conveyor system designed to transport containers of sample liquids between various operating stations. Known conveyor systems or tracks travel in a circuit so that the containers with the sample liquids pass through the operating stations in sequential order. Thus, the sample liquid may pass through a reagent filling station, mixing station, reaction forming station, detection and analysis station, etc. One such automated clinical analyzer is described in U.S. Pat. No. 4,066,412, assigned to DuPont. In the DuPont system, however, the conveyor transports test packs for analysis in one direction only wherein the test packs, once inserted into the apparatus, must pass through without subsequent access before analysis occurs. In this regard, there is limited or minimal flexibility in the types of chemical tests which can be performed on an automated analyzer which relies on a sequential-station transport system.
In performing tests on various liquids, such as the biological liquids mentioned above, it is often desirable to test these samples after one or more reaction mixtures have taken place. For example, many automated analyzers rely on light or radiant energy to obtain information about the characteristics of the sample under analysis. Fluorescence, light scatter, absorption and other light-related parameters are detected and assessed with respect to the constituents of the sample under analysis. To place the sample in proper condition for such analysis, for example, surface preparation of cells to be immunofluorescently labeled, one or more reaction mixtures in reaction vessels might be necessary. Moreover, time may be required between different reaction mixtures so that sufficient incubation may occur for adequate preparation. For this type of testing in an automated analyzer, access to the sample liquid may be required a number of times after the sample has been placed into the apparatus. Thus, instead of loading the sample into the apparatus and obtaining sequential testing, such as in the apparatus described above, a storage vehicle might be required so that subsequent access to the sample liquid may be available. Such an instrument for access to the sample liquid or for subsequent reaction mixtures is sometime referred to as a random access analyzer. One such random access analyzer presently available is known as the TDX analyzer, sold by Abbott Laboratories, Chicago, Illinois. Random access analyzers also process different kinds of assays in any order.
Another feature which is common to presently available sequential and random access analyzers is the inclusion of the various reagents within the apparatus itself or placed near the apparatus for piping thereinto. Liquid reagents, in bulk form, are selected for the various types of tests which are to be performed on the sample liquids, and are stored in or near the apparatus. Reagent delivery units, such as pumps or the like, along with valves, control mechanisms and pipes are included in these automated analyzers so that different reagents may be mixed according to the type of test to be performed. A typical automated analyzer which includes the storage of bulk reagents is described in U.S. Pat. No. 4,483,927. Of course, as bulk reagents are stored or associated with the automated analyzer by pipes and pumping, the apparatus becomes more complex, particularly with respect to operation, maintenance and cost. Furthermore, the possibilities of error and miscalculation are increased due to the many and different reagents immediately available for forming different reaction mixtures in a single test.
The goal of automated random access analysis of samples, combined with an apparatus constructed in uncomplicated fashion, along with simplification of operator interface, still remains in the field of automated chemical analyzers. Previously described analyzers, and others which are presently known and available, have not completely satisfied the aforementioned goal. Even those automated analyzers which provide random access are still rather cumbersome or complicated, or include the storage of bulk reagents and attendant piping and valves for the different mixtures of liquids. The present invention is directed to achieving the goals set forth above.